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Circadian Rhythm Entrainment

Sync with the sun

Problem it solves

Helps manage personal energy for sustained performance

Best for

Individuals who want to improve their sleep and energy levels

Not ideal for

Those who have irregular schedules or live in areas with limited sunlight

Overview

Why this framework exists

The circadian rhythm is the internal clock that regulates our sleep-wake cycle and is influenced by exposure to light. Entraining our circadian rhythm to the solar day can improve our sleep, energy, and mood. This framework involves getting morning sunlight and avoiding bright light in the evening to synchronize our internal clock with the external environment.

Core principles

3 total
  1. Exposure to natural light is essential for regulating our circadian rhythm.
  2. Avoiding bright light in the evening can help synchronize our internal clock with the external environment.
  3. Getting morning sunlight can improve our sleep, energy, and mood.

Steps

3 steps
  1. Get Morning Sunlight
    Exposure to natural light in the morning helps regulate our circadian rhythm. Spend at least 10-15 minutes outside in the morning, or open your curtains to let sunlight in.
    Pro tipTry to get outside in the morning, even if it's just for a short walk.
    WarningAvoid using screens or artificial light sources in the morning, as they can suppress melatonin production.
  2. Avoid Bright Light in the Evening
    Avoiding bright light in the evening can help synchronize our internal clock with the external environment. Use dim red lights or nightlights instead of bright white lights.
    Pro tipTry using blue light filtering glasses or apps that filter out blue light from screens.
    WarningAvoid using screens or artificial light sources at least an hour before bedtime.
  3. Use Artificial Light Sources Judiciously
    If you need to use artificial light sources, use them judiciously. Avoid using them in the evening, and opt for dim red lights or nightlights instead.
    Pro tipTry using smart light bulbs that can adjust their color temperature and brightness based on the time of day.
    WarningBe cautious when using artificial light sources, as they can disrupt our circadian rhythm if not used properly.

Checklist

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Examples

2 cases
Example 1: Getting Morning Sunlight

John started getting outside in the morning for a 10-minute walk. He noticed an improvement in his sleep and energy levels within a week.

OutcomeImproved sleep and energy levels
Example 2: Avoiding Bright Light in the Evening

Sarah started using dim red lights in the evening instead of bright white lights. She noticed an improvement in her sleep quality and mood within a few days.

OutcomeImproved sleep quality and mood

Common mistakes

3 traps
Not Getting Enough Morning Sunlight
Not getting enough morning sunlight can disrupt our circadian rhythm and lead to sleep, energy, and mood problems.
Using Screens or Artificial Light Sources Too Close to Bedtime
Using screens or artificial light sources too close to bedtime can suppress melatonin production and disrupt our circadian rhythm.
Not Being Consistent with Our Light Exposure
Not being consistent with our light exposure can disrupt our circadian rhythm and lead to sleep, energy, and mood problems.

Origin story

How this framework came to be

The concept of circadian rhythm entrainment has been studied for decades, and research has shown that exposure to natural light is essential for regulating our internal clock. Dr. Samer Hattar's work has contributed significantly to our understanding of the importance of light in regulating our circadian rhythm.

Source

Traced to primary
Source · PODCAST
Essentials: Timing Light for Better Sleep, Energy & Mood | Dr. Samer Hattar
Andrew Huberman · 2025
Open source →